Is my HVAC Guy correct? 2 systems instead of 1 system with Dampers - Home Energy Pros2015-03-31T21:27:47Zhttp://homeenergypros.lbl.gov/forum/topics/is-my-hvac-guy-correct-2-systems-instead-of-1-system-with-dampers?commentId=6069565%3AComment%3A140085&feed=yes&xn_auth=noSounds about right. In SoFla,…tag:homeenergypros.lbl.gov,2013-11-10:6069565:Comment:1405582013-11-10T03:24:28.187ZCurt Kinderhttp://homeenergypros.lbl.gov/profile/CurtKinder
<p>Sounds about right. In SoFla, heat might be needed just 10-20 days per year with an energy cost of $50-100</p>
<p>In NoFla, heat is needed intermittently in November and March, consistently Dec-Feb.</p>
<p>Sounds about right. In SoFla, heat might be needed just 10-20 days per year with an energy cost of $50-100</p>
<p>In NoFla, heat is needed intermittently in November and March, consistently Dec-Feb.</p> So in my $1000/$1080 scenario…tag:homeenergypros.lbl.gov,2013-11-10:6069565:Comment:1404922013-11-10T03:19:45.501Ztedkiddhttp://homeenergypros.lbl.gov/profile/tedkidd
So in my $1000/$1080 scenario, grid heat would have to cost a couple hundred a year before the reversing valve justified the efficiency loss in cooling..?<br/>
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Guess climates that don't usually have heating, recommending heat pumps not warranted.<br/>
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BOB, you may want to talk to the dry climate guys (Healy, MacFarland, Chitwood...), they've done extensive measuring of btu loss of duct at different delivery temps.
So in my $1000/$1080 scenario, grid heat would have to cost a couple hundred a year before the reversing valve justified the efficiency loss in cooling..?<br/>
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Guess climates that don't usually have heating, recommending heat pumps not warranted.<br/>
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BOB, you may want to talk to the dry climate guys (Healy, MacFarland, Chitwood...), they've done extensive measuring of btu loss of duct at different delivery temps. I have not; all my residentia…tag:homeenergypros.lbl.gov,2013-11-10:6069565:Comment:1406342013-11-10T03:10:19.515ZCurt Kinderhttp://homeenergypros.lbl.gov/profile/CurtKinder
<p>I have not; all my residential clients get HP since we have enough of a heating season to justify the expense.</p>
<p>I think you could safely figure the efficiency hit at 5-10%</p>
<p>I have not; all my residential clients get HP since we have enough of a heating season to justify the expense.</p>
<p>I think you could safely figure the efficiency hit at 5-10%</p> Not saying we don't need any…tag:homeenergypros.lbl.gov,2013-11-09:6069565:Comment:1405562013-11-09T17:00:38.853ZBob Blanchettehttp://homeenergypros.lbl.gov/profile/BobBlanchette
<p>Not saying we don't need any heat in the 40's, but heat loss is relatively low. Once the furnace has recovered from night setback (we setback for comfort reasons more than saving energy) it's done for the day. We've only started hitting the high 30's for morning lows in Oklahoma, it will be interesting to see what happens once winter gets here.</p>
<p>I'm with you on the "stupid pet tricks". People turn their heat to 72-75 in the morning then run the AC in the afternoon of the same…</p>
<p>Not saying we don't need any heat in the 40's, but heat loss is relatively low. Once the furnace has recovered from night setback (we setback for comfort reasons more than saving energy) it's done for the day. We've only started hitting the high 30's for morning lows in Oklahoma, it will be interesting to see what happens once winter gets here.</p>
<p>I'm with you on the "stupid pet tricks". People turn their heat to 72-75 in the morning then run the AC in the afternoon of the same day.</p>
<p>I have concerns about ductwork losses when running low BTU outputs. Our ductwork is in the attic and is of decent tightness (not perfect, but better than most). Does running low delta T cause more "loss"? If ductwork looses 5 degrees due to running through unconditioned space wouldn't that hurt the 90F discharge temps more than a 110F discharge temp of the air handler?</p> Bob and Curt, sorry my posts…tag:homeenergypros.lbl.gov,2013-11-09:6069565:Comment:1404902013-11-09T16:23:09.681Ztedkiddhttp://homeenergypros.lbl.gov/profile/tedkidd
<p>Bob and Curt, sorry my posts left the cascade I know it makes following the conversational thread frustrating and confusing - ipad does not want to reply in line. </p>
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<p>Bob: "<span> We have to get down into the 30's before the heat runs much."</span></p>
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<p><span>What does that mean? Seriously, you aren't suggesting that there is no load on residential structures at 40f, are you? </span></p>
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<p><span>If you look at consumption I think you'll find that most of it…</span></p>
<p>Bob and Curt, sorry my posts left the cascade I know it makes following the conversational thread frustrating and confusing - ipad does not want to reply in line. </p>
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<p>Bob: "<span> We have to get down into the 30's before the heat runs much."</span></p>
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<p><span>What does that mean? Seriously, you aren't suggesting that there is no load on residential structures at 40f, are you? </span></p>
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<p><span>If you look at consumption I think you'll find that most of it occurs above 30 for most of the country. So maybe stepping back and asking: "WHY DO <span> We have to get down into the 30's before the heat runs much" would open up another area to consider. </span></span></p>
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<p><span><span>If cycling on and off, overheating air, duct, and house and shutting off are inefficient, what is happening at 30 and above if your equipment "doesn't run much"? </span></span></p>
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<p><span><span>Furthermore is it comfortable to heat that way? I think it is not, and so people bump thermostats, use space heaters, overheat parts of their homes (even opening window) in an attempt to get other parts comfortable. Stupid Pet Tricks - we've done them and seen them. </span></span></p>
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<p><span><span>So I go back to the idea that having lots of stages is good for efficiency and comfort. I've sold LOTS of hybrids and I FOLLOW UP. Reports from happy clients about amazing comfort and amazing energy savings. </span></span></p>
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<p><span><span><a href="https://lh5.googleusercontent.com/-IDvMgPUJ8j0/Un5gvFNM3WI/AAAAAAAAnkg/l2jhovm1HzQ/w784-h482-no/Picasa+3+222013+50127+PM.jpg" target="_blank"><img src="https://lh5.googleusercontent.com/-IDvMgPUJ8j0/Un5gvFNM3WI/AAAAAAAAnkg/l2jhovm1HzQ/w784-h482-no/Picasa+3+222013+50127+PM.jpg?width=400" width="400" class="align-full"/></a></span></span></p>
<p><span><span>One trick I use is "please send pictures of <a href="http://bit.ly/meterpictures" target="_blank">your meter</a>". This saves a fair amount of time understanding savings: <a href="http://bit.ly/meterpictures" target="_blank">http://bit.ly/meterpictures</a></span></span></p>
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<p><strong>Curt, have you run the number on SEER savings from HP to straight AC? I need to factor that into my designs so people understand there is a small sacrifice in efficiency, and how that might translate to $. </strong></p>
<p></p> EER and SEER do track each ot…tag:homeenergypros.lbl.gov,2013-11-09:6069565:Comment:1406312013-11-09T16:19:36.539ZBob Blanchettehttp://homeenergypros.lbl.gov/profile/BobBlanchette
<p>EER and SEER do track each other until EER hits about 12-13. EER then stops about 13 while SEER continues to climb. Multistage certainly makes sense for zoned operation. Forcing full output into 1/2 the ductwork rarely will perform well.</p>
<p>"Bigger is better" is a hard mentality to break and the equipment is sized based on low stage with stage 2 as "reserve capacity". Rarely will you find 14+ SEER systems installed that are less than 3 tons capacity, regardless of what the load is. The…</p>
<p>EER and SEER do track each other until EER hits about 12-13. EER then stops about 13 while SEER continues to climb. Multistage certainly makes sense for zoned operation. Forcing full output into 1/2 the ductwork rarely will perform well.</p>
<p>"Bigger is better" is a hard mentality to break and the equipment is sized based on low stage with stage 2 as "reserve capacity". Rarely will you find 14+ SEER systems installed that are less than 3 tons capacity, regardless of what the load is. The 2ton 14.5SEER I installed summer of 2012 had a mfg date of 2009 on it. The supply house said they don't sell many high SEER low tonnage units.</p> A 75 degree room may have 77-…tag:homeenergypros.lbl.gov,2013-11-09:6069565:Comment:1407192013-11-09T14:04:41.408ZCurt Kinderhttp://homeenergypros.lbl.gov/profile/CurtKinder
<p>A 75 degree room may have 77-78 degree air into ceiling returns. Add a bit of duct leakage from a warm attic or garage and 80 is not unreasonable.</p>
<p>I will not further quibble with you over SEER parameters - my overall stance is that it is useful for comparison, just like MPG ratings. If my AO was in the desert southwest, I might pay more attention to EER. Besides, EER and SEER tend to track each other more or less, with EER running 75-80% of SEER.</p>
<p>Where high SEER systems really…</p>
<p>A 75 degree room may have 77-78 degree air into ceiling returns. Add a bit of duct leakage from a warm attic or garage and 80 is not unreasonable.</p>
<p>I will not further quibble with you over SEER parameters - my overall stance is that it is useful for comparison, just like MPG ratings. If my AO was in the desert southwest, I might pay more attention to EER. Besides, EER and SEER tend to track each other more or less, with EER running 75-80% of SEER.</p>
<p>Where high SEER systems really shine is during part load, low stage operation. We try to design zoned systems to keep a system in low gear more often by prioritizing different parts of the home during different times of day.</p>
<p>I'd be curious to review data supporting the premise that high SEER systems are more often oversized - do you have any?</p> I have a hard time believing…tag:homeenergypros.lbl.gov,2013-11-09:6069565:Comment:1405552013-11-09T13:44:33.686ZBob Blanchettehttp://homeenergypros.lbl.gov/profile/BobBlanchette
<p>I have a hard time believing a 5 degree increase on return air temp due to ductwork when it's 82 outdoors. You would be looking at a 10F+ increase on 95F days if the ductwork was that leaky.</p>
<p>Getting high SEER ratings without increasing EER is done mostly by reduction in cycling losses. Unfortunately the high SEER systems tend to be the ones most oversized which negates much of the real world savings...</p>
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<p>I have a hard time believing a 5 degree increase on return air temp due to ductwork when it's 82 outdoors. You would be looking at a 10F+ increase on 95F days if the ductwork was that leaky.</p>
<p>Getting high SEER ratings without increasing EER is done mostly by reduction in cycling losses. Unfortunately the high SEER systems tend to be the ones most oversized which negates much of the real world savings...</p>
<p></p> While I agree that EER is use…tag:homeenergypros.lbl.gov,2013-11-09:6069565:Comment:1407182013-11-09T13:19:34.868ZCurt Kinderhttp://homeenergypros.lbl.gov/profile/CurtKinder
<p>While I agree that EER is useful, SEER is also useful for comparison. The 80 degree EAT is not intended to reflect thermostat setpoint but instead to compensate for leakage into return air ductwork, AHU's outside conditioned envelope.</p>
<p>Everybody THINKS about AC whenever it is 90+ outside, but bin data shows that systems in the eastern half of the country spend many more hours dealing with humidity and 75-85 degree outdoor temps.</p>
<p>A brief look at my Carrier xls suggests that HPs…</p>
<p>While I agree that EER is useful, SEER is also useful for comparison. The 80 degree EAT is not intended to reflect thermostat setpoint but instead to compensate for leakage into return air ductwork, AHU's outside conditioned envelope.</p>
<p>Everybody THINKS about AC whenever it is 90+ outside, but bin data shows that systems in the eastern half of the country spend many more hours dealing with humidity and 75-85 degree outdoor temps.</p>
<p>A brief look at my Carrier xls suggests that HPs lose 1/2 to 3/4 EER point over comparable ACs.</p>
<p>Accumulator would have a small impact, and I'm not sure crankcase heaters figure into SEER or HSPF calculations.</p>
<p>So my advice to clients with NG for heat would likely run to straight cool - lower installed cost, higher operational efficiency, less complexity.</p> I never have bought into the…tag:homeenergypros.lbl.gov,2013-11-09:6069565:Comment:1406292013-11-09T12:32:56.587ZBob Blanchettehttp://homeenergypros.lbl.gov/profile/BobBlanchette
<p>I never have bought into the whole SEER thing, EER is what I'm concerned about. Most people keep their AC @ 75, not 80. Adding 15 degrees puts you at a 90 degree outdoor temperature which is very realistic. The 2 degree difference that SEER uses only puts you at 77 outdoors. AC's spend a LOT more time running @ 90F+ outdoors than they do at 77F or less. How much of a hit does a HP take vs. straight cool when it comes to EER?</p>
<p>As far as utility strain …</p>
<p>I never have bought into the whole SEER thing, EER is what I'm concerned about. Most people keep their AC @ 75, not 80. Adding 15 degrees puts you at a 90 degree outdoor temperature which is very realistic. The 2 degree difference that SEER uses only puts you at 77 outdoors. AC's spend a LOT more time running @ 90F+ outdoors than they do at 77F or less. How much of a hit does a HP take vs. straight cool when it comes to EER?</p>
<p>As far as utility strain <a href="http://www.ogepet.com/programs/smarthours.aspx" target="_blank">It's 2-7pm weekdays during the summer</a> that our grid works the hardest. The winter load doesn't even show up on the radar even with all the 20KW air handlers running. Too many homes have gas heat.</p>
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